﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;


namespace KingsSharp.Common.Extensions
{
    /// <summary>
    /// 随机数<see cref="Random"/>类型的扩展辅助操作类
    /// </summary>
    public static class RandomExtensions
    {
    /// <summary>
    /// 返回随机布尔值
    /// </summary>
    /// <param name="random"></param>
    /// <returns>随机布尔值</returns>
    public static bool NextBoolean(this Random random)
    {
        return random.NextDouble() > 0.5;
    }

    /// <summary>
    /// 返回指定枚举类型的随机枚举值
    /// </summary>
    /// <param name="random"></param>
    /// <returns>指定枚举类型的随机枚举值</returns>
    public static T NextEnum<T>(this Random random) where T : struct
    {
        Type type = typeof(T);
        if (!type.IsEnum)
        {
            throw new InvalidOperationException();
        }
        Array array = Enum.GetValues(type);
        int index = random.Next(array.GetLowerBound(0), array.GetUpperBound(0) + 1);
        return (T)array.GetValue(index);
    }

    /// <summary>
    /// 返回随机数填充的指定长度的数组
    /// </summary>
    /// <param name="random"></param>
    /// <param name="length">数组长度</param>
    /// <returns>随机数填充的指定长度的数组</returns>
    public static byte[] NextBytes(this Random random, int length)
    {
        if (length < 0)
        {
            throw new ArgumentOutOfRangeException("length");
        }
        byte[] data = new byte[length];
        random.NextBytes(data);
        return data;
    }

    /// <summary>
    /// 返回数组中的随机元素
    /// </summary>
    /// <typeparam name="T">元素类型</typeparam>
    /// <param name="random"></param>
    /// <param name="items">元素数组</param>
    /// <returns>元素数组中的某个随机项</returns>
    public static T NextItem<T>(this Random random, T[] items)
    {
        return items[random.Next(0, items.Length)];
    }

    /// <summary>
    /// 返回指定时间段内的随机时间值
    /// </summary>
    /// <param name="random"></param>
    /// <param name="minValue">时间范围的最小值</param>
    /// <param name="maxValue">时间范围的最大值</param>
    /// <returns>指定时间段内的随机时间值</returns>
    public static DateTime NextDateTime(this Random random, DateTime minValue, DateTime maxValue)
    {
        long ticks = minValue.Ticks + (long)((maxValue.Ticks - minValue.Ticks) * random.NextDouble());
        return new DateTime(ticks);
    }

    /// <summary>
    /// 返回随机时间值
    /// </summary>
    /// <param name="random"></param>
    /// <returns>随机时间值</returns>
    public static DateTime NextDateTime(this Random random)
    {
        return NextDateTime(random, DateTime.MinValue, DateTime.MaxValue);
    }

    /// <summary>
    /// 返回DateTime yyyy-MM-dd的时间字符串、为null时返回空
    /// </summary>
    /// <param name="date"></param>
    /// <returns></returns>
    public static string GetDateYYYYMMDD(this DateTime? date)
    {
        if (date == null)
        {
            return "";
        }
        else
        {
            return date.Value.ToString("yyyy-MM-dd");
        }
    }

    /// <summary>
    /// 获取指定的长度的随机数字字符串
    /// </summary>
    /// <param name="random"></param>
    /// <param name="length">要获取随机数长度</param>
    /// <returns>指定长度的随机数字符串</returns>
    public static string GetRandomNumberString(this Random random, int length)
    {
        if (length < 0)
        {
            throw new ArgumentOutOfRangeException("length");
        }
        char[] pattern = new char[] { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };
        string result = "";
        int n = pattern.Length;
        for (int i = 0; i < length; i++)
        {
            int rnd = random.Next(0, n);
            result += pattern[rnd];
        }
        return result;
    }

    /// <summary>
    /// 获取指定的长度的随机字母字符串
    /// </summary>
    /// <param name="random"></param>
    /// <param name="length">要获取随机数长度</param>
    /// <returns>指定长度的随机字母组成字符串</returns>
    public static string GetRandomLetterString(this Random random, int length)
    {
        if (length < 0)
        {
            throw new ArgumentOutOfRangeException("length");
        }
        char[] pattern = new char[] { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L',
            'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };
        string result = "";
        int n = pattern.Length;
        for (int i = 0; i < length; i++)
        {
            int rnd = random.Next(0, n);
            result += pattern[rnd];
        }
        return result;
    }

    /// <summary>
    /// 获取指定的长度的随机字母和数字字符串
    /// </summary>
    /// <param name="random"></param>
    /// <param name="length">要获取随机数长度</param>
    /// <returns>指定长度的随机字母和数字组成字符串</returns>
    public static string GetRandomLetterAndNumberString(this Random random, int length)
    {
        if (length < 0)
        {
            throw new ArgumentOutOfRangeException("length");
        }
        char[] pattern = new char[] { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 
            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
            'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };
        string result = "";
        int n = pattern.Length;
        for (int i = 0; i < length; i++)
        {
            int rnd = random.Next(0, n);
            result += pattern[rnd];
        }
        return result;
    }
    }
}
